1. Field of the Invention
This invention relates to an eye fundus observation apparatus which can reduce the flare from the cornea or the crystalline lens of an eye to be examined created during the observation of the fundus of the eye and which enables even a small pupil to be observed at a wide angle of view, and more particularly to an eye fundus camera.
2. Description of the Prior Art
A sectional view of an eye as observed through a prior art apparatus of this type is shown in FIG. 1 of the accompanying drawings. A prior art apparatus is known in which light-intercepting members are provided at positions substantially conjugate with the cornea 1 and the front surface of the crystalline lines 2 of an eye to be examined in order that light-intercepting portions 10 and 20 for eliminating flare may be formed on the cornea 1 and the front surface of the crystalline lens 2 (which is also substantially coincident with the position of the pupil) as shown in FIG. 1. In this apparatus, an observation opening is formed at a position conjugate with the cornea 1 of the eye being examined and as a result, the light beam in the portion shown by hatching in the figure provides an observation light. In FIG. 1, it is the condition for eliminating the flare by the reflected light from the cornea 1 and the front surface of the crystalline lens 2 that the observation light beam does not swell out of the light-intercepting portions 10 and 20.
Accordingly, if an attempt is made to increase the observation angle of view, the light-intercepting portion 20 on the front surface of the crystalline lens 2 must be made large. However, the maximum light beam is limited by the iris 3 of the eye and therefore, if the light-intercepting portion 20 is made large, the quantity of illuminating light will be decreased. Also, where the iris 3 is small, the observation opening is shut out by the iris 3 and the fundus of the eye cannot be observed at a wide angle of view.
On the other hand, an eye fundus camera in which a light-intercepting portion is also formed on the rear surface of the crystalline lens 2 of the eye shown in FIG. 1 to further eliminate the reflection on the front surface of the crystalline lens 2 and the position conjugate with the observation opening is provided at the position of the pupil (the opening of the iris 3) is known as U.S. Pat. No. 4,146,310. In this camera, however, if the angle of view becomes wider, both of the light-intercepting portion on the cornea and the light-intercepting portion on the rear surface of the crystalline lens must be made larger and in that case, the quantity of illuminating light is decreased to about the same degree as in the case of FIG. 1 and thus, the inverse proportional relation between the increase in angle of view and the decrease in quantity of illuminating light is still left to be solved.